Abstract

The growth temperature of spacer layers (SPLs) is investigated as a means to obtain identical layers for multilayerquantum dot(QD) structures. A QD structure with SPLs served as a model system. It is found that the growth temperature of the SPLs has pronounced effects on both the structural and optical properties of the QDs. For SPLsgrown at a low temperature of , dislocations are observed in the second and subsequent layers, a result of significant surface roughness in the underlying spacer layer. However by increasing the growth temperature to for the final of the SPLs, a much smoother surface is achieved, allowing the fabrication of essentially identical, defect free QD layers. The suppression of defect formation enhances both the room-temperature photoluminescence efficiency and the performance of multilayerQD lasers. An extremely low continue-wave room-temperature threshold current density of is achieved for an as-cleaved device with emission at and ground state operation up to .

Received 30 March 2004Accepted 25 May 2004Published online 02 August 2004

Acknowledgments:

This work is supported by the U.K. Engineering and Physical Sciences Research Council (EPSRC) Grant No. GR/S49308/01 and the European Commission GROWTH programme NANOMAT project, Contract No. G5RD-CT-2001-00545.